AKSA's Lender Preamp with 40Vpp Output

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#282
AKSA said:
BV,

Best option is to use balanced transformers, made by Sowter, Jensen, and Lundahl. They are expensive, but the best to use because they give galvanic isolation, guarantee to stop earth loop which make hum.

Hugh
Click to expand...

@ BV

To expand on the options, since you are in the US, you may find Cinemag transformers at a better price. Still expensive of course, but good performance. Something like a CMLI-15-15B if you want a 1:1 transformer.
 
#283
Group Buy status update.

JPS64 -2 sets w/ SMT daughterboards, Paid
*Algar Emi - 1 set, TH, Invoice sent
Redarc12 - 1 set, TH, Paid
CFT - 1 set, TH, Paid
Jacques Antoine - 1 set TH, Paid
Silasmellor - 1 set THT, Paid
Bvtrinh- 1 set TH, Paid
*ggetzoff - 1 set TH, Need PayPal address
tubesguy - 1 set TH, Paid
Aatto - 1 set SMT, Paid
*Mordikai - 1 set TH, Need PayPal address
*Johnny2Bad 1 set TH; 1 set SMT, Invoice sent
*vvs07 - 2 sets TH, Need PayPal address
*Fabian85 - 1 set SMT, Need PayPal address
PCGAB - 1 Set(MB) with SMT boards, Paid
*Harry3 - 1 set MB plus TH, Need PayPal address
*meanman64 - 1 set MB plus THT, need PayPal address
Wayne1 - 1 set TH, Paid
*obh - 1 Set(MB) plus TH, Invoice Re-sent
*PJN - 1 set TH, Need PayPal address
*manniraj - 1 set TH, Invoice sent
Erik777 - 1 set TH, Paid
Zman01 - 1 set SMT, Paid
AKSA - 1 set SMT, Paid
xrk971 - 1 set SMT, Paid
Click to expand...

The asterisks above (*) indicates members who need to respond.
Thanks to all the folks who have responded and deposited payment.
 
#285
GB Status Update

JPS64 -2 sets w/ SMT daughterboards, Paid
*Algar Emi - 1 set, TH, Invoice sent
Redarc12 - 1 set, TH, Paid
CFT - 1 set, TH, Paid
Jacques Antoine - 1 set TH, Paid
Silasmellor - 1 set THT, Paid
Bvtrinh- 1 set TH, Paid
*ggetzoff - 1 set TH, Need PayPal address
tubesguy - 1 set TH, Paid
Aatto - 1 set SMT, Paid
*Mordikai - 1 set TH, Need PayPal address
*Johnny2Bad 1 set TH; 1 set SMT, Invoice sent
*vvs07 - 2 sets TH, Need PayPal address
*Fabian85 - 1 set SMT, Need PayPal address
PCGAB - 1 Set(MB) with SMT boards, Paid
*Harry3 - 1 set MB plus TH, Need PayPal address
*meanman64 - 1 set MB plus THT, need PayPal address
Wayne1 - 1 set TH, Paid
obh - 1 Set(MB) plus TH, Paid
PJN - 1 set TH, Paid
manniraj - 1 set TH, Paid
Erik777 - 1 set TH, Paid
Zman01 - 1 set SMT, Paid
AKSA - 1 set SMT, Paid
xrk971 - 1 set SMT, Paid
spind - 1 set TH, Paid
Click to expand...

* indicates response needed. Thank you.

Update on the use of this preamp as a headphone amp: more listening confirms it is a superb headphone amp. Very clean low distortion sound, dynamic and engaging. Absolutely quiet silent when no signal present. No hum or hiss of any sort. The Toshiba 2SA1837 is a superb output transistor. I believe much of the sound quality is attributable to this finest of Toshiba’s audio BJT ever made. The TH version of the daughter board can readily accept the 2SA1837 vs the KSA1381 and with modification of two other resistors, you have a superb headphone amp. An extra TH set of daughterboards may be just the thing here.
 
Last edited:
#287
@maty tinman

TKD (40€) or RK (4€) potentiometer and you choose what you want equipped.

JP
 

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#291
Hi X,

or drill carefully 3 holes for signal in existing pads (signal and soldering on bottom side) and the 2 mechanical grounded pads (soldering on top side). I´ve done this operation on breadboard.

I could supply the template.

JP
 
#294
I have been buying the blue ones but they seem to only put out 45v. I just ordered these which can do a true 50v (reportedly). They are a bit more compact too. Will have to see what noise performance is once I get it.

Here are the blue ones:
DC/DC Boost Converters 8-32V 12V Step-up to 24v 9-46V 150W 8A 36V Driver Parts | eBay

Here are the newer metal PCB ones that go to 50v:
DC DC boost converter Constant Current Mobile Power supply 250W 10A LED Driver | eBay

250W CV/CC Car Notebook Power Supply LED Boost Driver Step-Up Module DC 8.5V-48V | eBay
 
#295
Thank you!

lehmanhill said:
@ BV

To expand on the options, since you are in the US, you may find Cinemag transformers at a better price. Still expensive of course, but good performance. Something like a CMLI-15-15B if you want a 1:1 transformer.
Click to expand...

Thank you! I am currently using those cinemags with my DAC and they work well. At roughly 70 dollars a piece along with the output transformers, it will probably cost more than twice the cost for the boards and parts. However, that is the nature of this hobby.
 
#297
bvtrinh said:
Thank you! I am currently using those cinemags with my DAC and they work well. At roughly 70 dollars a piece along with the output transformers, it will probably cost more than twice the cost for the boards and parts. However, that is the nature of this hobby.
Click to expand...

Certainly you could build two sets of this preamp to handle balanced drive for less than the cost of a pair of Cinemags.
 
#298
JPS64 said:
Hi X,

or drill carefully 3 holes for signal in existing pads (signal and soldering on bottom side) and the 2 mechanical grounded pads (soldering on top side). I´ve done this operation on breadboard.

I could supply the template.

JP
Click to expand...

Hi JP,
They were able to halt the production - please get me the revised Gerbers with RK09 holes and I will redo the order.
Thanks,
X
 
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